Problem: If $x \otimes y = 6x-2y$ and $x \triangleleft y = 2x-3y$, find $-3 \otimes (-4 \triangleleft -3)$.
Explanation: First, find $-4 \triangleleft -3$ $ -4 \triangleleft -3 = (2)(-4)-(3)(-3)$ $ \hphantom{-4 \triangleleft -3} = 1$ Now, find $-3 \otimes 1$ $ -3 \otimes 1 = (6)(-3)-(2)(1)$ $ \hphantom{-3 \otimes 1} = -20$.